Implementer sub-agent's final-gate checklist does not reliably enforce project lint at deny-warnings level

## Summary
Under strict TDD, the `implementer` sub-agent's "final gate before you finish" is expected to include: full test suite green, project lint clean at deny-warnings level, format clean, no stray `todo!()`/`unimplemented!()` outside declared out-of-scope surfaces, and pushed to origin. In practice — with an explicit dispatch instruction naming the lint invocation and "do not `#[allow]` around real issues" — the implementer completed the phase and pushed a branch containing two `-D warnings` lint errors introduced by its own wiring seam edits. Downstream orchestrator-spawned verification caught them, but had that verification not been run, the errors would have reached adversarial convergence.

## Proposed remediation
1. The implementer sub-agent's final-gate section should REQUIRE the project's lint invocation at deny-warnings level (Rust: `cargo clippy --all-targets --workspace -- -D warnings`; Go: `golangci-lint run`; TypeScript: `eslint --max-warnings 0`; etc.) and STOP with a reported failure list if it fails, before claiming done.
2. The dispatch template for implementer should treat lint-at-deny-warnings as a first-class exit gate on par with the test suite, not as an aspirational bullet.

## Impact
Overclaimed completion consumes downstream adversarial pass budget on defects that a language-native lint would have caught in seconds. The blocker is small (two auto-deref rewrites), but the ceremony to remediate it — verification dispatch + remediation dispatch + re-push + adversary re-run — is the tax.